Fix failing GCP tests

[denis256]

Noticed that different GCP tests still periodically fail, with the same error:

Failed
    compute_test.go:155: Launching new Compute Instance terratest-fabj54
TestGetAndSetMetadata 2022-05-28T20:08:55Z retry.go:91: Attempting to request a Google OAuth2 token
TestGetAndSetMetadata 2022-05-28T20:08:55Z compute.go:606: Successfully retrieved default GCP client
    compute_test.go:206: Error launching new Compute Instance: googleapi: Error 400: Invalid value for field 'resource.machineType': 'zones/europe-west8-a/machineTypes/f1-micro'. Machine type with name 'f1-micro' does not exist in zone 'europe-west8-a'., invalid

TestGetRandomRegionExcludesForbiddenRegions 2022-05-28T19:48:57Z region.go:67: Using Region australia-southeast1
    compute_test.go:155: Launching new Compute Instance terratest-4pmcyu
TestGetPublicIpOfInstance 2022-05-28T19:48:58Z retry.go:91: Attempting to request a Google OAuth2 token
TestGetPublicIpOfInstance 2022-05-28T19:48:58Z compute.go:606: Successfully retrieved default GCP client
    compute_test.go:206: Error launching new Compute Instance: googleapi: Error 400: Invalid value for field 'resource.machineType': 'zones/europe-west8-c/machineTypes/f1-micro'. Machine type with name 'f1-micro' does not exist in zone 'europe-west8-c'., invalid

Links:

https://app.circleci.com/pipelines/github/gruntwork-io/terratest/1010/workflows/54650e5e-d053-4a01-9e44-42d356088503/jobs/7726/tests#failed-test-0

https://app.circleci.com/pipelines/github/gruntwork-io/terratest/1011/workflows/7216ccde-e07b-4d69-a8c7-1d999baa31cb/jobs/7733